New Zealand and Australian media suggested the debris was from a Russian satellite expected to enter the atmosphere later in the day.

But the US space agency Nasa said it was more likely to have been meteors.

'40 second margin'

The Lan Airbus A340 had just entered New Zealand airspace as it approached Auckland's airport when the debris shot by.

The pilots reported the near-miss to air traffic controllers, reportedly saying the noise of the debris breaking the sound barrier could be heard above the roar of his aircraft's engines.

The New Zealand Herald newspaper calculated the debris missed the jet by a margin of 40 seconds.

The plane landed safely and continued to its final destination in Sydney, Australia, a short while later.

Initial media reports in New Zealand said the debris was thought to be the remains of a Russian satellite.

New Zealand air traffic control officials had been warned by Russian authorities that a spacecraft was due to fall into the Pacific Ocean on Wednesday.

But the debris was spotted by the pilots 12 hours earlier than the time advised by the Russians.

An orbital debris expert at Nasa told Associated Press news agency that he had checked with the Russians and that their vessel - a spacecraft resupplying the International Space Station - had fired its re-entry rockets 12 hours after the Chileans reported the near miss.

The Nasa expert, Nicholas Johnson, said no other space junk was expected to be re-entering atmosphere at that time so the pilots probably saw a meteor.